Jump to content


Photo

what is the shutter speed equivalent............


  • Please log in to reply
6 replies to this topic

#1 Chris Burke

Chris Burke
  • Basic Members
  • PipPipPipPip
  • 1675 posts
  • Boston, MA

Posted 30 September 2007 - 08:18 PM

.....of a 15 degree shutter angle in Super 16? I would think it is a pretty quick shutter, good for capturing fast motion with sharp images.
  • 0

#2 Nick Mulder

Nick Mulder
  • Basic Members
  • PipPipPipPip
  • 1023 posts
  • Other
  • Auckland, New Zealand

Posted 30 September 2007 - 08:50 PM

Either I am bout to get a lesson or you are -

I think there is something wrong with your understanding of shutter angles ...

Your shutter speed or exposure time (which is a more accurate term prone to less confusion) is dependent on both the shutter speed and shutter angle ...

To calculate your exposure time per frame find the % the shutter is open per frame - ie. in your case 15/360 = 0.04166666667 ~ %4.2

So for whatever fps you shoot at the shutter will be open for %4.2 of one frame cycle - for eg. 24fps:

one frame = 1/24sec = 0.04166666 ~ 42ms (the same answer as before that for some reason may become clear with some more input from other posters?)

so anyway, the exposure is %4.2 of 0.04166666 = ie. 0.04166666 * 0.04166666
= 1/576 of a sec - which is as you say "a pretty quick shutter, good for capturing fast motion with sharp images."

I'm not sure what 'equivalent' you are after though ... super16 or any other aspect/format has nothing to do with it


Maybe you mean in lieu of an adjustable shutter, what fps would give me a relative shutter angle of 15deg in a 180deg shutter camera ???? (along with all the extra redundant frames) - the mafamatatics are as follows ...

(2*(1/576))^-1 = 288 fps (of which you'd have 12 'streams' of 24fps each with a 15deg shutter angle a 1/12 of a cycle phase apart to choose from, to put it simply you'd be shooting 12x as much film as you needed)
  • 0

#3 Dominic Case

Dominic Case
  • Basic Members
  • PipPipPipPip
  • 1357 posts
  • Other
  • Sydney Australia

Posted 30 September 2007 - 10:24 PM

I think Nick's first answer is what you are looking for.

At 24 fps, the shutter angle, as a proportion of 360deg, gives you the exposure time as a proportion of 1/24th sec.

So a conventional 180deg shutter is open for 180/360 = 1/2 the time, that is 1/2 x 1/24th = 1/48th sec

A 15deg shutter would be open for 15/360 = 1/24th of the time, that is 1/24 x 1/24th = 1/576th sec.

From a still camera perspective that's only moderately fast, but it's still much shorter than the conventional motion picture 1/48th sec.

But while each individual frame might render fast-moving action a lot sharper, you will now have a longer gap in between them. Instead of a gap of 1/48th sec between each frame, you now have a gap of 23/24 x 1/24th - very nearly 1/25th sec, nearly twice as long as if you were running at the conventional 24fps speed. If the action you are shooting is fast action, then objectes will have moved even further in that time. This results in a jerky, stroboscopic effect. Filmmakers often go to considerable troulbe to re-introduce motion blur if it's missing for this or any other reason, so as to produce a more satisfactory result.
  • 0

#4 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19769 posts
  • Cinematographer
  • Los Angeles

Posted 30 September 2007 - 10:52 PM

A good example of the jerky, strobey motion of a 45 degree shutter at 24 fps, check out "Saving Private Ryan" and parts of "Gladiator".

So 15 degrees would look quite bizarre...

Since 24 fps is a fairly low frame rate in order to create the illusion of continuous motion, a certain amount of motion blur in each frame is actually needed or else you sense just how few frames there are sampling the motion.
  • 0

#5 Nick Mulder

Nick Mulder
  • Basic Members
  • PipPipPipPip
  • 1023 posts
  • Other
  • Auckland, New Zealand

Posted 30 September 2007 - 11:16 PM

I have some test footage here that was shot 15fps with the shutter synced to a photographic flash - although i dont know the exact flash duration wikipedia tells me a typical photographic flash duration is around 1/3000sec

mafamatatics: (X/360)*(1/15) = 1/3000 X = ~ 0.6 deg

It was a test for a music vid I plan to do with dance strobes in place of the photoflash so i can get a proper 25fps without the capacitor/timing pooping itself ...

Its pretty choppy - but hard to really tell because of A. the 15fps speed factor on playback at 24fps in projection and B. the short duration of the takes as the photoflash would deplete itself within 20 frames or so
  • 0

#6 Stephen Whitehead

Stephen Whitehead
  • Basic Members
  • PipPipPip
  • 124 posts
  • Cinematographer
  • Toronto, Canada

Posted 14 October 2007 - 10:54 PM

A good example of the jerky, strobey motion of a 45 degree shutter at 24 fps, check out "Saving Private Ryan" and parts of "Gladiator".

So 15 degrees would look quite bizarre...

Since 24 fps is a fairly low frame rate in order to create the illusion of continuous motion, a certain amount of motion blur in each frame is actually needed or else you sense just how few frames there are sampling the motion.


Was all of "Saving Private Ryan" shot at 45 degrees? or just the battle scenes?

Steve
  • 0

#7 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19769 posts
  • Cinematographer
  • Los Angeles

Posted 15 October 2007 - 01:01 AM

Was all of "Saving Private Ryan" shot at 45 degrees? or just the battle scenes?

Steve


Just where you see the effect of it.
  • 0


Abel Cine

Ritter Battery

Aerial Filmworks

Paralinx LLC

Broadcast Solutions Inc

Media Blackout - Custom Cables and AKS

Opal

Visual Products

Technodolly

Rig Wheels Passport

Gamma Ray Digital Inc

Willys Widgets

CineLab

Wooden Camera

rebotnix Technologies

Metropolis Post

CineTape

The Slider

Tai Audio

FJS International, LLC

Glidecam

Tai Audio

Technodolly

Aerial Filmworks

CineTape

Paralinx LLC

Abel Cine

Willys Widgets

Ritter Battery

Wooden Camera

Media Blackout - Custom Cables and AKS

FJS International, LLC

Broadcast Solutions Inc

Glidecam

Rig Wheels Passport

Opal

CineLab

Visual Products

Metropolis Post

rebotnix Technologies

The Slider

Gamma Ray Digital Inc